The known methods for synthesis of Latanoprost (see B. Resul et al., J. Med. Chem., 1993, 36, 243) include the stage of reducing of lactone-group of the compound [20] with excess of diisobutylaluminum hydride (DIBAL-H) at −72-−80° C. to give the compound [11b] (Scheme 1): 
However, this method is problematic as it is difficult to scale-up this highly exothermic reaction at such low temperature conditions. Furthermore, it was feared that increasing of temperature during DIBAL-H addition may lead to undesired processes in reduction of product [11b].